I general better AVR handle low ohms speakers better.
Frequency response is often printed in the spec's generally don't mean a lot. Quality not quantity is what you want. In theory the human ear can hear between 20hz and 20khz. More likely many can't hear much over 16khz when older. Thats not really an issue and the areas of the frequency spectrum affect use differently, see below.
Sub bass is 20hz to 60hz. Music wise a bass guitar would struggle to get to 41hz and in any case hard for us to hear due to what know as Fletcher Munson Curves. The frequency is best handled with a subwoofer to shake us as much anything else, so great for movies.
Bass is 60hz to 250hz Important area for many as the rhythm come from this range
250hz to 500hz Lower Mid range and cover by many instruments
500hz to 2khz Mid range, defines how prominent an instrument is
2khz - 4 khz Upper Midrange Human ear very sensitive to this spectrum
5khz - 6khz Affects the perception of clarity
6khz - 20khz Affects the perception of brilliance and sparkle and composed of harmonics
Regardless of spec sheets and all. Good speakers try and handling the 60-15khz range well. The more you spend the wider the frequency band gets that they cover well. Based on above how much really benefits what your listening too and lower distortion just as important.